1. Field
This document relates to a stereoscopic (i.e., three-dimensional (3D) image display capable of displaying a stereoscopic image by using a display device that displays left-eye image data and right-eye image data based on time division and active shutter glasses including a left-eye shutter and a right-eye shutter alternately turned on and off so as to be synchronized with left-eye and right-eye data of the display device, and a driving method thereof.
2. Related Art
A stereoscopic (or 3D) image display is divided into a device using a stereoscopic technique and a device using an autostereoscopic technique.
The stereoscopic technique, which uses a parallax image of left and right eyes of a user with a high stereoscopic effect, includes a glass method and a non-glass method which have been put to practical use. In the glass method, a left and right parallax image is displayed on a direct view-based display device or a projector by changing a polarization direction of the left and right parallax image, and a stereoscopic image is implemented by using polarization glasses or liquid crystal shutter glasses. In the non-glass method, generally, an optical plate such as a parallax barrier or the like for separating an optical axis of the left and right parallax image is installed in front of or behind a display screen.
U.S. Pat. No. 5,821,989 and US Laid Open Publication No. US2008022949A1 are known to disclose an example of the glass type stereoscopic image display.
FIGS. 1 and 2 are schematic views of a glass type stereoscopic image display. As illustrated, the part seen in black of a liquid crystal shutter glasses (ST) represents a shutter blocking light that proceeds toward an observer (i.e., viewer), and the part seen in white of the liquid crystal shutter glasses (ST) represents a shutter allowing transmission of light toward the observer.
FIG. 1 illustrates a time-division operation of a left/right image when an impulse type display device is selected in the glass type stereoscopic image display. In the impulse type display device such as a cathode ray tube (CRT), immediately after data is completely written in a scanning direction, data of each pixel is erased.
In the stereoscopic image display illustrated in FIG. 1, during an odd-numbered frame period, the left eye shutter of the liquid crystal shutter glasses (ST) is open, and left-eye image data (RGBL) are sequentially scanned on the impulse type display device (DIS1). During an even-numbered frame period, the right-eye shutter of the liquid crystal shutter glasses (ST) is open and right-eye image data (RGBL) are sequentially scanned on the impulse type display device (DIS1). Accordingly, the observer can view only a left-eye image during the odd-numbered frame period and a right-eye image during the even-numbered period, feeling solidity.
FIG. 2 illustrates a time-division operation of a left/right image when a hold type display device is selected in the glass type stereoscopic image display. In the hold type display device such as a liquid crystal display (LCD) device, data written in pixels are maintained until such time as data is written at a first line during a next frame period following a response completion time point after the data is written at the entire pixels due to response time delay characteristics.
In the stereoscopic image display illustrated in FIG. 2, during the odd-numbered frame period, the left-eye shutter of the liquid crystal shutter glasses (ST) is open and left-eye image data (RGBL(Fn)) of nth frame (n is a positive integer) are sequentially scanned on a hold type display device (DIS2). While the left-eye shutter of the liquid crystal shutter glasses (ST) is open, some pixels, to which the left-eye image data (RGBL(Fn)) of the nth frame have not been written yet in the hold type display device (DIS2), maintain right-eye image data (RGBR(Fn−1)) which had been already charged in (n−1)th frame. Accordingly, the observer can view an image of the right eye image data (RGBR(Fn−1) of the (n−1)th frame with his left eye, as well as the left-eye image data (RGBL(Fn)) of the nth frame during the nth frame.
In the stereoscopic image display illustrated in FIG. 2, during (n+1)th frame period, the right-eye shutter of the liquid crystal shutter glasses (ST) is open and right-eye image data (RGBR(Fn)) of (n+1)th frame are sequentially scanned on the hold type display device (DIS2). While the right-eye shutter of the liquid crystal shutter glasses (ST) is open, some pixels, to which the right-eye image data (RGBR(Fn)) of the (n+1)th frame have not been written yet in the hold type display device (DIS2), maintain left-eye image data (RGBL(Fn)) which had been already charged in nth frame. Accordingly, the observer can view an image of the left eye image data (RGBL(Fn) of the nth frame with his right eye, as well as the right-eye image data (RGBR(Fn)) of the (n+1)th frame during the (n+1)th frame.
As noted in FIG. 2, when the hold type display device (DISP2) is used in the glass type stereoscopic image display, the observer can feel a pseudo-stereoscopic vision at a time when the left-eye image is changed to the right-eye image or at a time when the right-eye image is changed to the left-eye image.
Thus, in order to improve the degradation of picture quality due to the response time delay of the stereoscopic image display as shown in FIG. 2, US Laid Open Publication NO. 2007022949A1 discloses a technique of addressing data more quickly than the related art on a liquid crystal panel without increasing a frame rate and extending a vertical blanking period. Also, this publication proposes a method of opening liquid crystal shutter glasses (ST) during a time period obtained by subtracting a liquid crystal response time from the extended vertical blanking period. In proposed method, the vertical blanking period without data is lengthened and an opening duration of the liquid crystal shutter glasses is reduced, making an observer feel flickering. In addition, constructive interference occurs between light that transmits through the liquid crystal shutter and ambient light according to a correlation between an ON/OFF period of the liquid crystal shutter and that of the ambient light such as a fluorescent lamp, making the observer feel flicking more severely.